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Site Status

EPA completed the second five-year review at the Halby Chemical Site in September 2012. The remedy in place remains protective of human health and the environment.

Recent monitoring of Site conditions has revealed elevated levels of arsenic moving into a stormwater drainage pond on the Halby Site, thought to originate from the nearby Interstate Route 495 Drainage Ditch (I-495 Ditch). A protective berm between this pond and the I-495 Ditch was constructed by the Site PRPs under EPA and DNREC oversight in October 2012.

EPA and DNREC are currently reviewing a PRP study of the I-495 Ditch and nearby area to determine the source of arsenic contamination.

Background

The nine-acre Halby Chemical Site is located in an industrialized section of Wilmington’s port area.

The major source of contamination on the site comes from a chemical production facility which operated from 1948 to 1980.

The facility had two abandoned buildings housing equipment and chemical storage. Wastewater from sulfur-based compounds were released into lagoons on site and then chemical effluent flowed into a tidal marsh leading to the Lobdell Canal and eventually into the Christina River located a half mile east of the site. The wastewater contaminated the lagoon, the marsh sediments, the subsurface soil and the underlying groundwater.

Eden Park, a residential community, is located about one-quarter mile west of the site, and about 2,500 people live within one mile. Residents receive potable water supplies from the Artesian Water Company, which draws water from supply wells located several miles away.

Cleanup History

NPL Listing History

EPA also addressed 600 small containers, 13 pressurized cylinders, 200 drums, 50 tanks and about 1,000 small containers mixed in with shallow soil.

All chemicals, which included carbon disulfide, thorium nitrate, mercury, ammonium thiocyanate, sulfide, cyanide and tetrachloroethene, in various containers were transported off-site for safe disposal.

In 1995, EPA issued a Unilateral Administrative Order to Witco Corp., a former owner/operator, requiring that the company erect a security fence around the site and treat the carbon disulfide soils in situ using a chemical oxidation process. The company successfully treated 11,000 cubic yards of soil by 1998.

A Record of Decision was issued in March 1998 outlining the additional cleanup remedies, which included capping soil; filling degraded wetlands; creating new wetlands at an off-site location to compensate for those lost; and institutional controls to prevent drinking water wells from being installed near the site.

All construction activities at the site were completed by 2002. Monitoring is ongoing to ensure the protectiveness of the cleanup remedies.

A five-year review was completed in September 2012. The review found the cleanup remedies to be protective of human health and the environment.

Contaminants and Risks

The groundwater is contaminated with carbon disulfide and metals, including arsenic and manganese. The lagoon and marsh sediments contained high levels of ammonia, arsenic, cadmium, copper and zinc. The surface water contained elevated levels of ammonia and heavy metals, including arsenic and lead. Arsenic was detected in the surface soil, and elevated levels of carbon disulfide in subsurface soil. The carbon disulfide in contaminated soil was treated with an innovative oxidation process, and longer poses a risk.

Community Information

Federal Register10/01/1999: Notice of Lodging of Consent Decree Relating to the Halby Chemical Superfund Site in Wilmington, New Castle County, Delaware, Under the Comprehensive Environmental Response, Compensation, and Liability Act